Field of the Invention
The present invention relates to an article of manufacture for conducting electrical signals. In particular, coaxial connectors such as F-Type connectors are equipped to reject RF ingress.
Discussion of the Related Art
FIGS. 1, 2, 3A-C, and 4 show prior art F-Type connectors. FIG. 1 shows a perspective view 100 of a prior art F female port 102 mounted to a wall plate 104. FIG. 2 shows a side view 200 of FIG. 1 revealing a coaxial cable 208 attached via an F male connector 206 to the F female port and leaving a room facing attachment end 204 of the F female port exposed to stray signals and/or RF ingress 210.
FIGS. 3A-C show a cross-sectional view 300A, side view 300B and a perspective view 300C of a prior art F splice with female ports 332, 334 at opposed ends. This splice provides interconnected internal contacts 312, 314 for engaging respective coaxial cable center conductors and a body 316 for engaging F male connector couplings such as threaded nuts and having electrical continuity with respective coaxial cable outer conductors. The splice body 316, such as a metallic body, provides for transport of a coaxial cable ground signal.
Threads 322, 324 at opposing ends of the splice tubular body 316 provide a means for engaging F male connector couplings at the splice end ports. The splice assembly end ports 332, 334 typically include an inwardly directed shallow metal lip 342 that may be rolled from the body or provided in another fashion, for example by fixing a shallow ring at the tube end. The lip provides peripheral support to a disc shaped end insulator 344 within the splice body. An insulator central aperture 346 is for receiving a center conductor of a coaxial cable. Behind this insulator is the internal contact 312 (314) mentioned above.
FIG. 4 shows a cross-sectional view of a bulkhead port 400. To the extent that connector internals are insertable from only a single end, the connector may be referred to as “blind.” The port has an F female port 432 at one end and a mount 450 at an opposed end. Similar to the splice above, the port includes an electrically conductive body 416, an internal contact 412 behind an insulator 444 held in place by a port end lip 442. An aperture 441 in the insulator provides for inserting a coaxial cable center conductor into the port contact 412 and body threads 422 provide for engaging an F male connector coupling such as a threaded nut.
Unlike the splice 300A-C, the bulkhead port 400 has a mount 450 at one end that may be separate from or include portions of a device/equipment bulkhead or portion(s) thereof. The mount supports the bulkhead port from a base 452. A contact 412 trailing portion 481 passes through a hole in a base insulator 456 and then through a hole 458 in the base. As may be required, the base is insulated from the contact by an air gap or by another means known to skilled artisans.
These prior art connectors may become the source of future problems as proliferation of RF devices such as cellular telephones crowd RF spectra and increase the chances RF ingress will adversely affect interconnected systems such as cable television and satellite television signal distribution systems.
Persons of ordinary skill in the art have recognized that in cable television and satellite television systems (“CATV”), reduction of interfering radio frequency (“RF”) signals improves signal to noise ratio and helps to avoid saturated reverse amplifiers and related optic transmission that is a source of distortion.
Past efforts have limited some sources of the ingress of interfering RF signals into CATV systems. These efforts have included increased use of traditional connector shielding, multi-braid coaxial cables, connection tightening guidelines, increased use of traditional splitter case shielding, and high pass filters to limit low frequency spectrum interfering signal ingress in active home CATV systems.
The F connector is the standard connection used for cable television and satellite signals in the home. For example, in the home one will typically find a wall mounted female F connector or a coaxial cable “drop” splitter or isolator for supplying a signal to the TV set, cable set-top box, or internet modem.
A significant location of unwanted RF signal and noise ingress into CATV systems is in the home. This occurs where the subscriber leaves a CATV connection such as a wall-mounted connector or coaxial cable drop connector disconnected/open. An open connector end exposes a normally metallically enclosed and shielded signal conductor and can be a major source of unwanted RF ingress.
As shown above, a CATV signal is typically supplied to a room via a wall mounted connector or in cases a simple “cable drop.” These and similar cable interconnection points provide potential sources of unwanted RF signal ingress into the CATV system. As will be appreciated, multiple CATV connections in a home increase the likelihood that some connections will be left unused and open, making them a source of unwanted RF ingress. And, when subscribers move out of a home, CATV connections are typically left open, another situation that invites RF ingress in a CATV distribution system.
Known methods of eliminating unwanted RF ingress in a CATV system include placing a metal cap over each unused F connector in the home or, placing a single metallic cap over the feeder F port at the home network box. But, the usual case is that all home CATV connections are left active, and when unused, open, a practice the cable television operators and the industry have accepted in lieu of making costly service calls associated with new tenants and/or providing the CATV signal in additional rooms.
The inventor's work in this area suggests current solutions for reducing unwanted RF ingress resulting from open connectors are not successful and/or not widely used. Therefore, to the extent the CATV industry comes to recognize a need to further limit interfering RF ingress into CATV systems, it is desirable to have connectors that reduce RF ingress when they are left open.
Prior art exists which attempts to accomplish this goal but is generally thought to be prohibitively expensive, impractical, or mechanically unreliable. For example, one prior art method disclosed in patent applications of the present inventor disconnects the center conductor contact when the F female is not connected to a male connector. Another method is disclosed in U.S. Pat. No. 8,098,113 where an electronic method differentially cancels noise common to both the center conductor and shield and requires an electric power source. These methods are relatively expensive compared with at least some embodiments of the present invention. They also have reliability limitations due to either of included mechanical or electrical elements.
Presently, it appears the industry has little interest in RF ingress reduction solutions similar to those proposed herein. However, in the inventor's view, there are good reasons to pursue the invention herein to maintain signal quality.